UV unwrapped object showing unwanted lines in Substance Painter
The problem is that there are there are overlapping areas in your UV map.  Thus, when you paint on one area in the texture, it affects the other portions of the UV map that overlap that same point.  You'll probably want to try using a different UV projection for the model.  Try out several options until you get a nice UV map that doesn't overlap.  Just note that some projections are view dependent.  So try going into a view that makes sense (like front view) before unwrapping.  You can also try electing edges in problematic areas and selecting Ctr+e -&gt; Mark Seam so that the UV map disconnects along that edge.  Once you got something that looks pretty good, you can head over to the &quot;Texture Paint&quot; mode to get a basic idea of how good the UV map will work before importing it into Substance Painter.
Hope that helps!